This invention relates to new stabilizer combinations, and to synthetic resin compositions, particularly olefin polymer, acrylic polymer, vinyl halide polymer, and polyamide compositions containing the same, and having as a result an increased resistance to deterioration in color and mechanical properties when exposed to light or heated at elevated temperatures of the order of 150.degree. C. and higher.
The pioneer disclosure of 2,2,6,6-tetramethylpiperidine-4-alcohol esters for stabilizing a polymer is believed to be by K. Murayama in U.S. Pat. No. 3,640,928 of Feb. 8, 1972. Murayama stabilized synthetic polymers including polyolefins, polyvinyl chloride, polyvinylidene chloride, polyurethane, and polyamide against photo- and thermo-deterioration by incorporating 0.01 to 5% by weight of the synthetic polymer of a piperidine derivative having the general formula: ##STR1## in which R.sub.1 and R.sub.2, which may be the same or different, each are an alkyl group such as methyl, ethyl, isopropyl or dodecyl, or they form, together with the carbon atom to which they are attached, a saturated alicyclic group such as ##STR2## OR A GROUP OF THE FORMULA ##STR3## n is an integer of 1 to 3 inclusive, and R.sub.3 is an acyl group.
Murayama characterized his piperidine derivative stabilizers as showing a high degree of stabilizing action on synthetic polymers against photo deterioration with no appreciable degree of coloring action on the polymers; they can be used together with plasticizers and other known stabilizers without coloring the polymers to be stabilized or reduction in their stabilizing ability; they show little thermal sublimation and exudation; and they exhibit excellent stabilizing action against thermo-deterioration as well as photo-deterioration Murayama further stated that if desired, two or more of the piperidine derivative may be used in admixture, and the piperidine derivatives may be used alone or in combination with other known stabilizers, fillers, pigments, and the like (see column 6, lines 14-16). While Murayama disclosed a very large number of piperidine derivative stabilizers and polymer compositions stabilized therewith, the only polymer composition disclosed by Murayama that contains stabilizers added to the piperidine derivative is a polyvinyl chloride stabilized with a combination of lead stearate, dibasic lead stearate and cadmium stearate.
The Murayama et al. patent has been followed by a large number of patent and literature disclosures by Murayama et al. and others of polymer stabilizer compounds including a 2,2,6,6-tetrasubstituted-4-piperidyl group in the molecular structure, of which the following selection is representative. Thus Murayama in U.S. Pat. Nos. 3,898,303 of Aug. 5, 1975 and 3,941,744 of Mar. 2, 1976 disclosed 2,2,6-6-tetramethylpiperidino-spiro-hydantoin derivatives. Murayama in U.S. Pat. No. 3,899,464 of Aug. 12, 1975 disclosed 2,2,6,6-tetramethylpiperidinospiro-1,3-dioxane compounds. Murayama in U.S. Pat. No. 3,933,735 of Jan. 20, 1976 disclosed 2,2,6,6-tetrasubstituted-4-piperidone derivatives.
Murayama in U.S. Pat. No. 3,940,363 of Feb. 24, 1976 disclosed a further variation in which two 2,2,6,6-tetrasubstituted-4-piperidyl groups are linked together via the ring nitrogen atom to a bivalent organic linking group.
Randell in published patent application Ser. No. B408,123 of Apr. 3, 1976 disclosed 2,2,6,6,-tetrasubstituted piperidine-4-ols with a 1 to 20 carbon atom organic substituent on the piperidine nitrogen.
C. Ramey in U.S. Pat. Nos. 3,920,661 of Nov. 18, 1975 and 3,939,163 of Feb. 17, 1976 disclosed 3 to 10 carbon atoms dicarboxylic acids and salts in which one carboxylic acid group is esterified with a 2,2,6,6-tetrasubstituted-4-hydroxy piperidine.
B. Cook in U.S. Pat. Nos. 3,929,804 of Dec. 30, 1975, and 3,939,168 of Feb. 17; 3,971,795 of July 27 and 3,998,784 of Dec. 21, 1976 disclosed 2,2,6,6-tetrasubstituted-4-piperidinoacetic acid esters, thiolesters, and amides and similar 4-piperidinoacetic acid compounds additionally substituted on the nitrogen atom of the piperidine ring with an organic group having 1 to 12 carbon atoms.
Throughout these disclosures, the emphasis is on the synthesis of new 2,2,6,6-tetrasubstituted piperidine compounds and the demonstration of their utility in stabilized synthetic resin compositions. Disclosure of additional stabilizing ingredients to be used in such resin compositions is either entirely absent or completely unspecific, embracing any and all known compounding ingredients without distinction. Typical of the latter kind of unspecific disclosure is that in Murayama U.S. Pat. No. 3,640,928 already cited, or the following statement by Cook (see column 7 lines 4 to 13 of U.S. Pat. No. 3,998,784):
Optionally, the composition of the invention may contain one or more further additives, especially those used in polymer formulations, such as antioxidants of the phenol or amine type, U.V. absorbers and light protectants, phosphite stabilisers, peroxide decomposers, polyamide stabilisers, basic co-stabilisers, polyvinyl chloride stabilisers, nucleation agents, plasticizers, lubricants, emulsifiers, anti-static agents, flame-protectants, pigments, carbon black, asbestos, glass-fibres, kaolin and talc. PA1 The present invention therefore includes binary, tertiary and multi-component compositions containing, as stabiliser, a compound of formula I together with one or more functional additives for polymers.
Following this statement, Cook recites 13 classes of phenolic antioxidants and one class of amine antioxidants, encompassing over 100 specifically named compounds; 8 classes of ultraviolet absorbers and light protectants encompassing over 50 specifically named compounds; phosphite stabilizers including two subclasses and 6 specifically named compounds; peroxide-decomposing compounds including two subclasses and 6 specifically named compounds; classes of polyamide stabilizers, polyvinyl chloride stabilizers, and basic co-stabilizers with 6 subclasses and 6 specifically named compounds.
In the only Examples where Cook discloses specifically the use of a 2,2,6,6-tetrasubstituted piperidine compound with another stabilizer, there are blended 38 parts of polypropylene with 0.076 parts of n-octadecyl-3-(4'-hydroxy-3',5'-t-butylphenyl)propionate and 0.19 part of one of five 2,2,6,6-tetrasubstituted piperidines. Light stability was measured by determining the exposure time for 50% loss of the initial tensile elongation. Heat stability was not measured. Nothing is said of any contribution to light stability by the added propionate.
As a convenient summary of much of the prior art of stabilizing polyolefins, polyvinyl chloride, and polyamides, the recitation from column 7 line 18 to column 13 line 29 of Cook U.S. Pat. No. 3,998,784 is here incorporated by reference.
Further perspective on the prior art of polymer stabilization can be had by consulting the disclosures of classes of stabilizers and individual members thereof by M. Minagawa in U.S. Pat. Nos. 3,733,288 of May 15, 1973 and 3,907,517 of Sept. 23, 1975 as well as the review by L. Nass in "Encyclopedia of Polymer Science and Technology" (N. Bikales, executive editor, J. Wiley-Interscience, New York) volume 12 (1970) pages 725-768.
D. Bown et al. in U.S. Pat. Nos. 3,510,507 of May 5, 1970 and 3,691,132 of Sept. 12, 1972 disclosed polyolefins stabilized with polyphosphites, polyphosphates, polyphosphonites, polyphosphonates, polyborates, polycarbonates, and polysilanes which are condensation products of a 4,4'-bisphenol with a condensing or linking agent which may be of the ester type, such as the esters of triaryl or mixed arylalkyl compounds, or the acid halide type. Bown's condensation product stabilizers have molecular weights between 600 to 8000 or higher and are described by the structural formula, ##STR4## where X is selected from the group consisting of ##STR5## --C--C, and C--A--C--where A is a C.sub.1 to C.sub.16 alkylene or an arylene; R', R", R'", and R"" are selected from the group consisting of hydrogen, C.sub.1 to C.sub.18 alkyls, and an aryl group; Y is selected from the group of ##STR6## where R is hydrogen, a C.sub.1 to C.sub.18 alkyl, or aryl; ##STR7## where m is 0 to 10, preferably 4 to 8, ##STR8## where A' is (CH.sub.2).sub.n --S--(CH.sub.2).sub.n or --(CH.sub.2).sub.n --S--(CH.sub.2).sub.m -- S--(CH.sub.2).sub.n where n is 0 to 10, preferably 2 and m is 0 to 10, preferably 5; ##STR9## where R is an alkyl, preferably methyl, and Z is ##STR10## where R', R", R'", R"", and X correspond respectively to the R', R", R'", R"", and X previously selected when n has a value from 1 to 15, or Z may be derived from the compound used to introduce Y into the product when n has a value from 2 to 15, for example --R or --OR where R is hydrogen, an alkyl, or aryl. When Y in the formula of Bown's stabilizer is ##STR11## the stabilizer is a type of hydroxyaryl phosphite. Similarly, when Y in the formula is ##STR12## the stabilizer is a hydroxyaryl carbonate.
Bown's condensation products are described as especially effective in high molecular weight solid polyolefins when used together with a dialkyl sulfide costabilizer such as dilauryl thiodipropionate, distearyl thiodipropionate, ditridecyl thiodipropionate, dicetyl sulfide, bis(tetradecylmercapto) paraxylylene, and 10,24-dithiotetracontane.
J. Floyd et al in German published application 2505071 of Aug. 14, 1975 abstracted in Chemical Abstracts 1976, Volume 84, abstract no. 5945f, disclosed low molecular weight polycarbonate esters of bisphenols such as 2,2-bis(3-t-butyl-4-hydroxyphenylpropane) and 4,4'-butylidene bis(6-t-butyl-3-methylphenol) prepared in such a way as to contain few or no free phenolic hydroxyl groups as being highly effective heat and light stabilizers for polyolefins and giving a synergistic effect with distearyl thiodipropionate, tris (nonylphenyl) phosphite, and distearyl pentaerythritoldiphosphite.